"Some of the most precious documents we possess about the Modern philosophers such as Descartes and Leibniz are the letters they wrote. To all and sundry. People who were asking them about their philosophy. Students they took on... And... I had this idea that if at some future date someone was going to collect my works, I wouldn't be embarrassed to see the letter, amongst those works..." Pathways to Philosophy: Seven Years On

Monday, May 6, 2013

Descartes' case for the existence of God

Thank you for your email of 18 December, with your essay for the University of London Modern Philosophy Descartes et. al. module, in response to the question, 'Did Descartes succeed in proving the existence of God?'

I am always a bit wary of questions that lack a specific focus, because they can be so easily misconstrued as invitations to waffle.

Obviously, the examiner wants you to give an exposition and critique of Descartes' two arguments for the existence of God, the argument from the idea of perfection (the 'causal argument'), and Descartes' version of the ontological argument.

If that's what the examiner wants, then you should use as few words as possible explaining Descartes' motivations, the nature and purpose of his Meditations, even the point about God being needed as a precondition for the possibility of knowledge of the external world. All this is dispensable -- unless, of course, you can show that the correctness of a particular interpretation of one or other of Descartes' arguments, as against competing interpretations, requires specific reference to this background information.

The Cartesian circle is likewise part of background information; unless you can make a case that Descartes way of laying out the causal or ontological arguments crucially depends upon a premiss whose weakness is exposed in the Cartesian circle. (I don't think so, but I would be willing to be proved wrong.)

With regard to the causal proof, you complain about Descartes' unquestioning adoption of Scholastic terminology in his distinction between 'formal' and 'objective' reality, but your objection is summed up the remarks, 'the causal principle and levels of reality argument... find little support today', and 'Modern science finds no issues with the idea of something coming from nothing.' Well, I would have at least attempted to dig a little deeper. Is there any way we can reformulate Descartes' argument without using Scholastic terminology? What's the basic idea?

It does not sound implausible to claim that I have the idea of 'other persons' because other persons actually exist. This is one possible line of argument in response to the problem of other minds. My idea of your being 'real' and not merely a physical entity whose external appearance is similar to my own, goes beyond anything that could be presented in experience. Where does this idea come from? One possible explanation is that the very process of being inducted into human culture involves participation in human relationships, and this explanation requires that others are 'human' (real subjects of experience) like me. (There is a connection here with Wittgenstein's argument against a private language. One early commentator, A.J. Ayer responded with a thought experiment of an infant brought up by robots who grows up believing, falsely, that the robots have minds.)

Or consider the idea of infinity as such. One line of argument in the philosophy of mathematics would be that the fact that we have this idea is proof that infinite sets actually exist. But do we have an idea of infinity, beyond the merely formal definition of 'an infinite set can be put into a 1-1 correlation with a proper subset'? (There is an excellent book on 'The Infinite' by A.W. Moore, Routledge.)

On the ontological argument, your objection is that 'the simple approach of using existence as a property of an object like colour is not reasonable'. I don't see this as such a problem. Let's invent a term, 'eggsists' which is defined in such a way that every statement of the form 'A eggsists' is true. To eggsist is to have any property, period. We can deal with Santa Claus by pointing out that statements with non-referential terms either create truth-value gaps (Strawson) or require analysis by means of Russell's theory of descriptions. If you *want* to say that 'Santa Claus doesn't exist' then you need to consider what it would take to satisfy the requirements for being Santa Claus. In other words, you are not talking about an entity, Santa Claus, but rather a description or cluster of descriptions and considering whether or not there is some (eggsisting) object which satisfies the description.

It is true that we need a 'second-order' notion of existence in order to formalize talk of 'satisfying descriptions' which can call exists (by contrast with eggsists). But none of this settles the question over the ontological argument.

What about the ontological argument? Here is one argument which looks somewhat stronger than the standard reading of the ontological argument, or at least worthy of respect:

1. We have an idea of 'God' such that no existing entity can be greater, in any respect.

2. Such an entity, if it exists, must exist in all possible worlds (otherwise an entity which existed in all possible worlds would be greater).

3. It is not impossible that God exists.

4. God exists in some possible world.

5. Therefore, God exists in all possible worlds.

This is just an example of a possible reading of the ontological argument. (No, it doesn't convince me either.) The point is that millions of words have been written on the ontological argument. The examiner is looking for something a bit more substantial than you give. Or alternatively choose a different question.

To repeat, the examiner is not interested in background information. They are looking for the analysis and critique of an argument (or, rather in this case two arguments) which directly engages with the question whether either argument has any claim to be persuasive.